Probé este codigo que encontre en la web y me funciono:
lcSize = JpgSize( )
? lcsize
FUNCTION JPGSize( pcFileName, pnWidth, pnHeight )
IF EMPTY( m.pcFileName)
pcFileName = GETFILE( "JPG", "Select JPG File:", "Get Size")
ENDIF
IF EMPTY( m.pcFileName)
RETURN ""
ENDIF
PRIVATE lnHandle, lcRetStr
lnHandle = FOPEN( m.pcFileName)
lcRetStr = ""
IF m.lnHandle > -1
PRIVATE lnFileSize, lnCounter, lcBytes
lnFileSize = FSEEK( m.lnHandle, 0, 2)
lnCounter = 0
= FSEEK( m.lnHandle, 0, 0)
FOR lnCounter = 1 TO m.lnFileSize - 2
lcBytes = FREAD( m.lnHandle, 3)
IF m.lcBytes = CHR(0) + CHR(17) + CHR(8) OR ;
m.lcBytes = CHR(0) + CHR(11) + CHR(8)
*
lcBytes = FREAD( m.lnHandle, 4)
EXIT
ELSE
= FSEEK( m.lnHandle, -2, 1)
ENDIF
ENDFOR
= FCLOSE( m.lnHandle)
pnWidth = ASC( SUBSTR( m.lcBytes, 3, 1)) * 256 + ;
ASC( SUBSTR( m.lcBytes, 4, 1))
pnHeight = ASC( SUBSTR( m.lcBytes, 1, 1)) * 256 + ;
ASC( SUBSTR( m.lcBytes, 2, 1))
lcRetStr = LTRIM( STR( m.pnWidth)) + "x" + LTRIM( STR( m.pnHeight))
ELSE
pnWidth = 0
pnHeight = 0
lcRetStr = ""
ENDIF
RETURN m.lcRetStr
ENDFUNC && JPGSize
